It is known to the art to produce shaped concrete materials by advancing concrete molding frames, feeding stiff-consistency concrete to the molding frames in motion, shaping the concrete in a required cross section, and discharging the shaped concrete pieces backwardly from the molding frames still in motion. This method, however, requires large, expensive facilities.
The inventors developed an apparatus for forming a strip of prestressed concrete material by causing a short upper mold to move on concrete placed in advance in a long lower mold. A patent application covering this invention was filed with Japanese Patent Office and has already been disclosed under Japanese patent application Disclosure No. 41218/1980. This apparatus makes use of one sliding upper frame which is provided with a scraper for smoothing concrete and an upper mold and which is adapted to be advanced while being shaken in its entirety. This apparatus is effective in forming flat concrete plates but is hardly suitable for forming concrete plates incorporating reinforcing ribs.
When stiff-consistency concrete is placed and set in an ordinary molding frame, it is exposed to vibration and pressure for as much time as is required. In the slide forming operation which is required to compress concrete to a required cross section simply by passing the upper mold, it is thought hardly practicable to place concrete uniformly in the thin plate portion and the thick rib portion. Hopes have nevertheless been entertained that this trouble might be solved by making improvements in the upper frame side.
The method for covering the lower mold of concrete with metal plates accurately and efficiently has remained to be perfected. The construction of rails for guiding the vibrating upper frame, the method for curing a strip of concrete product, and the method for cutting this strip into pieces of a desired size have room for further refinement.